Tamper protection device for protecting a field device against tampering

ABSTRACT

The invention relates to a tamper protection device for protecting a field device against tampering, comprising a carrier and at least one electronic memory, wherein the at least one electronic memory is disposed in at least one partial area on the carrier, and the at least one electronic memory stores at least one predefinable security information item, and wherein the at least one electronic memory is designed in such a way as to modify the predefinable security information item in the event of at least partial damage to the tamper protection device. The invention further relates to a method for producing a field device having a tamper protection device, to a field device comprising a tamper protection device, to a tamper protection system, and to the use of a tamper protection device.

The invention relates to a tamper protection device for protecting a field device against tampering, a method for manufacturing a field device with a tamper protection, a tamper protection system and uses of a tamper protection device.

Field devices are used in a variety of areas of technology, for example in the form of signal installations as traffic lights, railway signals or the like. Field devices are normally connected to a control device, for example a control station or similar in order to control the field devices using control signals. A field device of this type may, in particular, comprise a control computer to process the control signals, to which a configuration memory is connected. These two components are therefore essential for the control of the field device. The control computer can furthermore be connected to an input/output unit of the field device, via which sensor signals of additional sensors can be transferred, for example sensors which monitor a rotation speed of an actuator of the field device or similar. In addition, the field device also comprises a communication interface for communication with the control station.

In order to avoid manipulations on the field device and in particular on the control computer and the configuration memory, it has become known to the applicant that these two components are provided with a sealing compound, for example an epoxy resin or the like. Accessibility to the two components is thereby hindered and a certain tamper protection is achieved.

Due to the protection of the control computer and the configuration memory against tampering, the configuration data stored in the configuration memory, for example in particular cryptographic keys for the communication with the control station, are protected against manipulations or their manipulation is at least hindered.

An integrated circuit which has a tamper protection is, for example, the ATMEL AT98, the data of which are downloadable at http//www.datasheetarchive.com/AT98SC008CT-datasheet.html.

In addition, it has become known to the applicant to dispose sensors on the field device in order to detect a manipulation of the control computer or the configuration memory. These sensors may, for example, be disposed inside or outside a tamper-protected area. It has thus become known to the applicant, for example, to dispose a wire mesh in the tamper-protected area, said wire mesh being connected to a corresponding sensor to apply electrical signals to the wire mesh. If an attacker then carries out a manipulation on the control computer or on the configuration memory of the field device, for example by drilling into the sealing compound in order to achieve a contacting of the control computer and/or the configuration memory to read out data in order to be able to manipulate the latter, the wire mesh will, with a certain high probability, be destroyed. In order to achieve an effective tamper protection, a continuous monitoring of the wire mesh by the corresponding sensor is required for this purpose. Otherwise, an attacker could remove the wire mesh, for example if a device was switched off, could analyze the wire mesh and reconstruct an electrically equivalent wire mesh before putting the field device back into operation and before said device is connected to the control station. The field device itself and also the control station could not then detect whether or to what extent the field device has been manipulated.

A continuous monitoring also requires a corresponding energy supply, which incurs additional costs. Moreover, it is necessary to check the condition of the energy supply continuously in order to enable a reliable protection of the field device against tampering.

It has become known from U.S. Pat. No. 7,685,438 to introduce magnetic particles into a protective layer of an integrated circuit. The magnetic particles can be detected by sensors and a cryptographic key can be produced using the detected information relating to the magnetic particles. If the protective layer of the integrated circuit is removed, the information required to generate the cryptographic key is therefore also destroyed.

It has furthermore become known from US 2008/192240 to evaluate a characteristic property of an optical waveguide in order to detect a physical manipulation of the optical waveguide.

One object of the present invention is therefore to provide a simple and low-cost tamper protection device which, in particular even without an uninterrupted monitoring, reliably enables detection of a physical manipulation of a field device provided with the tamper protection device.

This object is achieved by a tamper protection device for protecting a field device against tampering, comprising a tamper protection carrier and at least one electronic memory, wherein the at least one electronic memory is disposed in at least one partial area on the tamper protection carrier and the at least one electronic memory stores at least one predefinable security information item, and wherein the at least one electronic memory is designed to modify the predefinable security information item in the event of an at least partial damage to the tamper protection device.

The object is similarly achieved by means of a method for manufacturing a field device with a tamper protection device as claimed in at least one of claims 1 to 6, comprising the steps of manufacturing the field device, manufacturing the tamper protection device, disposing the tamper protection device on the field device, and connecting the tamper protection device to a monitoring device to monitor the tamper protection device.

The object is similarly achieved by means of a field device comprising a tamper protection device as claimed in at least one of claims 1 to 6.

The object is similarly achieved by means of a tamper protection system comprising at least one field device, at least one tamper protection device as claimed in at least one of claims 1-6, at least one monitoring device, wherein the tamper protection device is disposed on the field device for the tamper protection, and wherein the monitoring device is connected to the tamper protection device.

Finally, the object is also achieved through the use of a tamper protection device as claimed in at least one of claims 1-6 in and/or on a field device, and the use of a tamper protection device as claimed in at least one of claims 1-6 as a security seal.

The advantage gained here is that a tamper protection device is thus provided which is irreparably destroyed in the event of a physical manipulation, for example a drilling into, breaking open or the like. The security information in the electronic memory of the tamper protection device at least partially destroyed by the physical manipulation can therefore no longer be reconstructed. In this way, a physical manipulation of a field device with a tamper protection device of this type is detectable on the basis of the destroyed security information. A further advantage is that a continuous or ongoing monitoring of the tamper protection is not necessary, since a physical manipulation is also subsequently detectable on the basis of the modified or destroyed memory content and therefore a changed security information item. Finally, a further advantage is that no complex sensor system, for example pressure sensors, radiation sensors, temperature sensors or similar needs to be provided, thereby reducing manufacturing costs.

Further features and advantages of the invention are described in the subclaims.

The tamper protection carrier is advantageously designed as a foil, in particular as a plastic foil. The advantage gained here is that the at least one electronic memory can thus be disposed on the tamper protection carrier in a simple and low-cost manner, and a simple arrangement of the foil, for example on a printed circuit board, is simultaneously enabled. The at least one electronic memory may, for example, be designed as an electronic circuit printed onto the foil. The memory may, in particular, be imprinted flatly on the foil, thus covering at least a partial area of the foil. Furthermore, the memory may be designed in a plurality of layers imprinted above one another and isolated from one another.

The foil can furthermore be glued onto a carrier, for example a printed circuit board. The foil can also be wrapped around the printed circuit board and glued or welded. A foil bonded with the printed circuit board can furthermore be protected by applied epoxy resin and/or can be molded in epoxy resin.

The at least one electronic memory is appropriately designed to store the security information permanently or modifiably. The advantage gained here is that, if the security information is permanently stored in the electronic memory, said information can be stored directly during the manufacture of the memory, for example by means of the aforementioned imprinting of the electronic circuit, in said memory, so that a simple and low-cost storage of the security information is enabled. If the security information in the at least one electronic memory is modifiable, for example during an operation of the field device, the security information can be recreated and/or overwritten daily, hourly, by the minute or the like. Moreover, a continuous overwriting of the electronic memory with new security information is also possible. In this way, the security can be even further increased, since, on the basis of the essentially constant updating of the at least one electronic memory, it can also be established when the respective security information was stored in the at least one electronic memory, and when a physical manipulation of the at least one electronic memory took place: following a physical manipulation of the tamper protection device, the security information can no longer be further modified, since the at least one electronic memory has been totally or partially destroyed. If it is simultaneously known which security information was written and when it was written into the at least one electronic memory, the time of the physical manipulation can then be determined.

The at least one electronic memory is advantageously designed to provide a second information item dependent on and different from the security information. In this way, for example on the basis of the security information, a cryptographic key can be generated directly and/or by means of a key derivation function and/or a cryptographic hash function, in particular SHA-1, SHA256, HMAC-SHA-1, HMAC-SHA256. This can be used, for example, in order to carry out a decryption of data of the field device and, alternatively or additionally, an error detection and/or an error correction method can be applied during the creation of the cryptographic key, so that modified content of a configuration memory of the field device is detectable and in particular at least partially correctable.

The security information can be designed as a digitally coded bit sequence.

The security information density of the security information appropriately has a size of at least 32 bits, in particular at least 64 bits, preferably at least 128 bits, appropriately at least 256 bits, in particular at least 512 bits, particularly preferably at least 1024 bits, in particular for each unit area, wherein the unit area is less than 5 cm², in particular less than 2.5 cm², preferably less than 1 cm², appropriately less than 5 mm², particularly preferably less than 1 mm² As a result, on the one hand, the security information stored in the at least one electronic memory is not feasibly guessable. Moreover, an even greater protection against physical manipulation is achieved, since, with a spatially small physical manipulation of the tamper protection device, many bits of the security information are already modified or destroyed due to the physical manipulation of the electronic memory.

A plurality of electronic memories are advantageously disposed, which are designed to provide a common security information item. In this way, the memory requirement of the electronic memories can be substantially reduced, so that said memories can be manufactured even more economically and reliably.

In the tamper protection system, the monitoring device is appropriately designed to check a security information item of the tamper protection monitoring device and de-activate or activate the field device depending on the result of the check.

The advantage thus gained, particularly if the monitoring device is disposed in the field device itself, is that the field device itself can change from an active to an inactive condition so that a further attack on the field device is further hindered for an attacker, if the check reveals a manipulation of the security information. The field device can then, for example, autonomously delete keys stored in a configuration memory or provide a status message and/or transmit it to a control station or permanently destroy electronic components of the field device by means of a short circuit in order to prevent an attack on said components.

Further features and advantages of the invention can be found in the following description of example embodiments with reference to the drawing.

In the drawing, in schematic form:

FIG. 1 shows a field device with a tamper protection device according to a first embodiment of the present invention; and

FIG. 2 shows steps of a method for manufacturing a field device with a tamper protection device according to the first embodiment.

FIG. 1 shows a field device with a tamper protection device according to a first embodiment of the present invention.

In FIG. 1, reference number 1 denotes a field device. The field device 1 comprises a carrier 2, for example in the form of a printed circuit board. A control computer 5, for example a CPU or the like, which is connected to a configuration memory 6 for exchanging data, is disposed on the carrier 2. Furthermore, the control computer 5 is connected via a line to a network module 8, which in turn provides an interface 9 for transmitting data to a control station, for example via Ethernet.

The control computer 5 is further connected via a line to an input/output unit 7. The input/output unit 7 is connected to sensors and/or actuators 10, for example temperature sensors, control elements, etc. If, for example, the field device 1 is designed as a signal installation for trains, the input/output unit can transfer corresponding commands to motors 10, etc., of the signal installation by means of the control computer 5. Simultaneously, a check can be carried out by means of the sensors 10 to determine whether the signal installation has properly carried out the instruction received from the control computer 5.

FIG. 1 furthermore shows a dotted, rectangular area which essentially covers the control computer 5 and the configuration memory 6. A tamper protection device 4 is disposed in this area. The tamper protection device 4 comprises a tamper protection foil 4 a as a tamper protection carrier, on which electronic memories 3 are disposed, in particular in a regular manner. The tamper protection foil 4 a with the electronic memories 3 is disposed in such a way that the electronic memories 3 completely cover the control computer 5 and the configuration memory 6 and thus provide a tamper protection for these two components. Respective interconnections of the individual electronic memories and at least one connection of the electronic memories 3 to an interface of the control computer 5 and/or the configuration memory 6, in order to be able to retrieve or read out the security information M stored in the electronic memories are not shown in FIG. 1. The configuration memory 6 and/or the control computer 5 can thereby read out the security information M of the electronic memories 3, for example via an I2C bus or SPI, and, for example depending on the read out security information item M or the read out security information items M, can create a cryptographic key which can be used to decrypt configuration data of the field device 1 stored in encrypted form in the configuration memory 6.

It is furthermore possible to design the tamper protection device 4 in such a way that it does not provide the memory content of the electronic memories 3 directly, but a value dependent thereon. Thus, for example, the tamper protection device 4 can be designed to carry out a processing step for the use of the security information M of the electronic memories 3, wherein the result of this processing step is then provided as security information M′. In this way, it is possible to carry out a challenge-response method, wherein the tamper protection device 4 provides a response which is dependent on data stored in the electronic memories 3 of the tamper protection device 4 and the challenge value transmitted to the tamper protection device 4. The response value may, for example, be an identical copy of the security information M′ provided by the tamper protection device 4, a checksum, in particular a CRC checksum or a hash value, for example SHA-1.

It is furthermore possible for the security information M stored in the electronic memories 3 to be randomly or pseudo-randomly generated.

FIG. 2 shows steps of a method for manufacturing a field device with a tamper protection device according to the first embodiment.

In FIG. 2, reference number S1 denotes the step of manufacturing the field device 1, reference number S2 denotes the step of manufacturing the tamper protection device 4, reference number S3 denotes the disposing of the tamper protection device 4 on the field device 1 and reference number S4 denotes the connection of the tamper protection device 4 to a monitoring device to monitor the tamper protection device.

To summarize, the invention has a plurality of advantages. The invention enables the detection of a physical manipulation of a field device without the need for a continuous monitoring. In this way, for example, no continuous power supply is required. In addition, the tamper protection device can also be simply and economically manufactured, for example by means of printable electronics and/or printable memory. A further advantage is that an extensive protection can also be achieved as a result. A further advantage is that a complex sensor system for detecting a physical manipulation is not required. In addition, an increased protection against physical manipulations is provided by the tamper detection device, beyond the tamper protection devices already known.

Although the present invention has been described above on the basis of preferred example embodiments, it is not restricted thereto, but is modifiable in a variety of ways. 

1. A tamper protection device (4) for protecting a field device (1) against tampering, comprising a tamper protection carrier (4 a) and at least one electronic memory (3), wherein the at least one electronic memory (3) is disposed in at least one partial area on the tamper protection carrier (4 a), and the at least one electronic memory (3) stores at least one predefinable security information item (M), and wherein the at least one electronic memory (3) is designed to modify the predefinable security information item (M) in the event of at an least partial damage to the tamper protection device (4).
 2. The tamper protection device as claimed in claim 1, characterized in that the tamper protection carrier (4 a) is designed as a foil, in particular as a plastic foil.
 3. The tamper protection device as claimed in claim 1, characterized in that the at least one electronic memory (3) is designed to store the security information (M) permanently or modifiably.
 4. The tamper protection device as claimed in claim 1, characterized in that the at least one electronic memory (3) is designed to provide a second information item dependent on and different from the security information (M).
 5. The tamper protection device as claimed in claim 1, characterized in that the security information (M) has a size of at least 32 bits, in particular at least 64 bits, preferably at least 128 bits, appropriately at least 256 bits, in particular at least 512 bits, particularly preferably at least 1024 bits, in particular for each unit area, wherein the unit area is less than 5 cm², in particular less than 2.5 cm², preferably less than 1 cm², appropriately less than 5 mm², particularly preferably less than 1 mm².
 6. The tamper protection device as claimed in claim 1, characterized in that a plurality of electronic memories (3) are disposed, which are designed to provide a common security information item (M′).
 7. A method for manufacturing a field device (1) with a tamper protection device, comprising the following steps: manufacturing (S1) the field device 1, manufacturing (S2) the tamper protection device (4), disposing (S3) the tamper protection device (4) on the field device (1) connecting (S4) the tamper protection device (4) to a monitoring device (5, 6) to monitor the tamper protection device (4)
 8. A field device (1) comprising: a tamper protection device for protecting the field device against tampering, the tamper protection device comprising: a tamper protection carrier (4 a) and at least one electronic memory (3), wherein the at least one electronic memory (3) is disposed in at least one partial area on the tamper protection carrier (4 a), and the at least one electronic memory (3) stores at least one predefinable security information item (M), and wherein the at least one electronic memory (3) is designed to modify the predefinable security information item (M) in the event of at an least partial damage to the tamper protection device (4).
 9. A tamper protection system, comprising at least one field device (1), at least one tamper protection device (4) as claimed in at least one of claims 1-6, at least one monitoring device (5, 6), wherein the tamper protection device (4) is disposed on the field device (1) for the tamper protection, and wherein the monitoring device (5, 6) is connected to the tamper protection device (4).
 10. The tamper protection system as claimed in claim 9, characterized in that the monitoring device (5, 6) is designed to check a security information item (M) of the tamper protection monitoring device (4) and to de-activate or activate the field device (1) depending on the result of the check.
 11. The use of a tamper protection device (4) as claimed in claim
 1. 12. The use of a tamper protection device (4) as claimed in claim 1 as a security seal. 